Voltage regulator



Dec. 28, 1954 s. sHERR VOLTAGE REGULATOR Filed March 9, 1954 IN V ENTOR. SOLOMON SHEER BY W ATTO NEY \7 VOLTAGE souzc:

United States Patent Ofiice 2,698,416 Patented Dec. 28, 1954 VOLTAGEREGULATOR Solomon Sherr, Tuckahoe, N. Y., assignor to General PrecisionLaboratory Incorporated, a corporation of New York Appiication March 9,1954, Serial No. 414,957

13 Claims. (Cl. 32322) This invention relates to direct-current powersupplies providing regulated output voltages. Such a supply usuallycomprises an alternating current source, a rectifier, and filter, withan electronic device for maintaining constant output voltage.

One form of regulating device employed in such a supply includes asensitive control element such as an electronic tube in series with theoutput terminals, and an amplifier sensitive to the output potential forcontrolling the sensitive control element. In addition a referencepotential is employed such as the potental drop across a voltageregulator tube, and it may be shown that some sort of referencepotential is required in every voltage regulator of this kind.

One purpose of voltage regulation is to keep the power supply outputvoltage constant. This function of regulation, constancy of outputvoltage, can be defined as the variation of output voltage divided bythe nominal or full-load output voltage. Alternatively the inputvolttage or its change may be the denominator. That is:

dE Regulatwn dB (2) in which E1 is the input voltage.

The smaller the value of the fraction the better the voltage regulationis said to be. Either load current change or input voltage change maytend to change the output voltage. The present invention reduces orsubstantially eliminates changes in output voltage due to either cause.

It is conventional in a power supply of the type under consideration toemploy a high vacuum electronic tube in series with the load, and toapply the regulatory effort to the control grid of this tube. However,obviously any device which controls electrical power by the applicationof smaller power may be employed, among such devices being transistors,saturable reactors, and amplidynes. It is also conventional in suchpower supplies to employ an electronic tube negative feed backamplifier. However it is obvious that in place of the electronic tubeamplifier a transistor amplifier may be employed with appropriatechanges in connections. The instant invention is concerned with thereference voltage required in the voltage regulator. In place of any ofthe conventional forms of reference voltage the instant inventionemploys a reference voltage depending on a voltage or current inherentlygenerated within the feedback amplifier. The magnitude of this inherentvoltage or current is completely or substantially independent of themagnitudes of all externally applied voltages excepting, in the case ofelectronic tube amplifiers, of the filament voltage. In general, themagnitude of the inherent voltage or current is dependent only upon thematerials employed in the construction of the electronic tube or of thetransistor.

The inherent voltage in the case of an electronic tube amplifier may bedesignated as the initial cathode potential and termed e. This potentialis the sum of the initial velocity potential, vi, due to thermal escapeof electrons from the cathode, and of the contact potential, Vcp, whichis in turn dependent upon the work function of the material of which thecathode is made. That is,

ticular transistor.

The inherent voltage 2 is made to produce a current drop across thisresistor which is ence voltage V.

In the case of transistors it is simpler to consider currents ratherthan voltages, and the inherent current employed to generate thereference voltage is described as the collector cutofi current, Inn.This current is that which flows in the collector circuit when theemitter current is zero, and is the result of an inherent property ofthe par- The inherent current is made to flow through a fixed resistor,and it is the resulting voltage drop across this resistor which isemployed as the reference voltage V0 in the transistor embodiment ofthis invention.

The general purpose of this invention is to provide a regulated powersupply including a feedback amplifier containing an inherent electricalmagnitude which serves to generate a reference magnitude.

Another purpose of this invention is to provide a regulated power supplyincluding an electronic tube feedback amplifier having an inherentinitial cathode potential, of which the reference potential is afunction.

employed as the refer- Another purpose of this invention is to provide aregulated power supply including a transistor feedback amplifier havingan inherent collector cutoff current, of which the reference potentialis a function.

A further understanding of this invention may be secured from thedetailed description and drawings, in which:

Figure 1 depicts a regulated voltage supply employing electronic tubesand embodying this invention.

Figures 2 and 3 depict a voltage regulator employing a transistorfeedback amplifier.

Figure 4 depicts a transistor voltage regulator employing a seriestransistor as the sensitive control element.

Referring now to Fig. 1, a source of voltage 11 in cludes a rectifierenergized by alternating current, and emits filtered direct currenthaving a potential E. This potential is applied to the voltage regulatorinput conductors 12 and 13, conductor 12 being positive. Conductor 12 isconnected through a series triode 14 to conductor 16 and thence to theregulated power supply output terminal 17, while conductor 13 isconnected directly to the other output terminal 18. A voltage divider 19and resistor 21 are placed in series across output terminals 17 and 18,so that a desired fraction of the output voltage E0 appears at thevoltage divider slider 22 in accordance with its manual adjustment. Thisvoltage divider 19 provides means for manually adjusting the outputvoltage E0 and also acts to correct for changes in output voltage whenreplacing tubes, caused by differences in individual tubecharacteristics.

The plate 23 of a triode 24 is connected to the positive regulatedconductor 16, while its grid 26 and cathode 27 are connected to slider22. The plate 28 of a triode amplifier 29 is connected to the positiveconductor 16 through-a resistor 31, and the cathode 32 is connected toslider 22. Grid 33 is grounded" to conductor 13. The output from plate28 is coupled through resistor 34 to the control grid 36 of anamplifier-inverter pentode 37. The cathode 38 of pentode 37 is connectedto the slider 39 of a voltage divider 41 for adjustment of bias voltageand plate current. The plate 42 is connected through resistor 43 to thepositive conductor 16. The output derived from the plate 42 is appliedto the control grid 46 of triode 14 through conductor 44.

In the operation of this circuit, changes of the potential of outputterminal 17 relative to terminal 18, whether due to changes in loadcurrent or to changes in input voltage, change the potential at theslider 22. This potential change is amplified in triode 29, amplifiedand inverted in pentode 37, and applied to the control grid 46 of triode14 in such sense that the voltage drop through of the voltagedrop Edacross the resistor 31 having resistance R which is due to e. That is:

in which lb is'the plate current of tube 29 and is a function of e. Thisis conventionally expressed as in which Eb is the plate potential, ,0.is the amplification constant and EclS the grid-cathode potential. Theplate current lb thus is due to three causes, and that part due tothe-initial cathode potential e may be termed la. It is the potentialdrop V in theplate resistor 31 due to la, which is-employed as thereference potential in this circuit. That V=IeR The quantity e has themagnitude of a volt or so. Although this is small compared to usualvalues of plate voltage, it is found that this fixed primary referencepo tential is large enough tolserve as the' source of a referencevoltage V in highly practical voltage'regulators.

The cathode of pentode ,37 of course generates an initial cathodepotential, but since it is in the second stage of amplification itseffect is negligible. The function of this tube is principally to invertthe signal, an even number of stages being necessary to apply the signalto the sensitive control tube 14in the right sense for regulation of theoutput voltage.

The contact potential, Vcp, being dependent on the work function of thematerial of the cathode 32, is highly dependent on the cathodetemperature. It is therefore desirable, in order to stabilize V, tosecure constancy of Vcp and therefore of e. In order to secure constancyof the contact potential Vcp in spite of fluctuations of filamentvoltage and other causes of temperature variation the triode 24 isemployed.

' In the operation the filament correction triode 24, is adjusted sothat its plate current is considerably higher than the plate current oftriode29, and causes a selected potential drop in voltage divider 19between slider 22 and conductor 13. If for any reason, suchas byincrease of filament current, the cathode 32 should increase intemperature, its potential will become more negative. But since cathode27 is heated by the same filament circuit its potential will alsodecrease and triode 24 will draw more current. The resulting increasedpotential drop through the lower part of voltage divider 19 will then,raise the potential of cathode 32 to neutralize the change made by thetemperature change. If the temperature of cathode 32 should decrease,the reverse effects will neutralize itstendency to increase inpotential.

Instead of returning the control grid 26 to the slider 22, it'may befound desirable to return it to some other point on the voltage divider19, depending on the relations between the characteristics of theparticular tubes employed as triodes 24 and 29.

The principles of this invention are embodied in the circuit of Fig. 2,in which unregulated filtered direct-current potential E1 is applied toinput terminals 47 and 48. A triode 49 in series with input terminal 47and output terminal 51 is employed as the sensitive control element, andinput terminal 48 is connected to output terminal 52'. A voltage divider3 and resistor 54in series across tthe output terminals 51 and 52 reducethe output potential E0 to a fraction suitable for feeding back to thesensitive control element 49, and provide means of adjustment. Thenegative feedback voltage amplifier is an n-p-n junctionjtransistor 56connected as a grounded or common emitter amplifier. One input isconnected from slider 57 of'v'oltage' divider 53 to the base terminal 58and the other input is through conductor 59 to the emitter terminal'61.' Positive potential is applied to the collector terminal 62 throughthe collector resistor 63, and output potential is taken from thecollector terminal and applied through conductor 64 to thecontrol grid66 of triode 49.

It is a property of transistors that a small current called thecollector cutoff current, 100, flows when the emitter current is zero.This collector cutolf current can be thought of as flowing at all timesin addition to other collector currents which flow in accordance withinput and output circuit potentials. The collector cutoff currentmagnitude is nearly independent of all applied potentials, and isernployed in this circuit as the source of the reference p'otentiali Thecollector cutoff current, flowing through the resistor 63, causes apotential drop Vc therein. It is this potential drop which is employedin this. circuit as the reference potential, existing at all times as apart of the potential applied to control grid 66.

In operation, if the output potential E0 should decrease, theemitter-to-base potential of transistor 56 is decreased. This causes thecollector current to decrease, reducing the potential drop in resistor63 and making control grid 66 less negative. The voltage drop acrosstriode 49 is thereby decreased, neutralizing the drop in outputpotential. If the output potential EU should tend to increase thereverse action ensues, against neutralizing the change in outputvoltage.

The reference potential dependent upon the collector cutoff current issmall, so that in some cases one feedback transistor amplifier is notsutficient to provide good regulation. In such cases more than one stageof feedback amplification may be used, an odd number of stages beingrequired if all transistors are of the same type or an even number ifthey are alternately of the n-p-n and p-n-p types. Fig. 3 illustratesthe latter situation.

In Fig. 3 the input terminals 47 and 48 are connected to the outputterminals 51 and 52 through series triode 49 as in Fig. 2, and thevoltage divider 53 and resistor 54 reduce the feedback signal. A p-n-pjunction transistor 67 has its base terminal 68 connected to the slider69 of voltage divider 53. The collector 71 is connected through acollector resistor 72 to output terminal 52 and the emitter 73 isconnected to output terminal 51. The output potential taken from thecollector 71 contains not only the amplified signal applied to the basebut also the reference potential consisting of the potential drop inresistor 72 due to the collector cutoff current. This output potentialis applied to the base terminal 74 of an n-p-n junction transistor 76having its collector 77 connected to output terminal 51 through resistor78 and its emitter 79 connected directly to output terminal 52.Connection is made between collector 77 and the control grid 81 oftriode 49.

A transistor may be substituted for the series triode employed in Figs.1, 2 and 3 as the sensitive control element, and when the seriestransistor is combined with a transistor feedback amplifier a voltageregulator employing only transistors results. Such a regulator isdepicted in Fig. 4. The input terminals 47 and 48 are connected to theoutput terminals 51 and 52 in series with an n-p-n junctiontransistor82, the collector 83 being connected to terminal 47 and the emitter 84being connected to output terminal 51. An n-p-n transistor 86 servesas'the negative feedback amplifier, its base 87 being connected to theslider 88 of voltage divider 89. Its emitter 91 is connected to outputterminal 52 and its collector 92 is connected through collector resistor93'to the positive input terminal 47. Connection of this resistor to theinput terminal instead of to the output terminal 51 is preferablebecause the potential between base and emitter of transistor 82 is verylow, which would necessitate a small value of collector resistor. Byconnecting the collector resistor to the collector 83 a large value ofresistance can be employed resulting in greater amplification and betterregulation.

What is claimed is:

1. A voltage-regulated power supply comprising, a

source of direct-current potential, a load circuit connected to saidsource, a control device having a control electrode for controlling anelectrical quantity existing between a pair of other electrodes, one ofsaid pair of electrodes being connected to said source and the other ofsaid pair of electrodes being connected to said load circuit, anamplifying device, a source of fixed primary reference potential, saidsource being an inherent part of said amplifying device, an impedanceconnected in series with said amplifier and a source of potential fordeveloping a potential drop in said impedance a portion of which resultsfrom the application of said fixed primary reference potential, saidportion of potential drop constituting the reference potential utilizedby the said power supply, means for applying a potential to saidamplifying device proportional to the potential applied to said loadcircuit, and means for applyingthe potential of said impedance to thecontrol electrode of said control device.

2. A voltage-regulated power supply comprising, a source ofdirect-current potential, a load circuit connected to said source, acontrol transducer having several electrodes including acontrolelectrode for controlling an electrical quantity existing betweena pair of other electrodes, said pair of electrodes being interposed inseries between said source and sail load, an electrical amplifyingdevice having at least one stage generating a fixed inherent electricalquantity, an impedance connected in series with said stage and a sourceof direct current whereby a potential drop is developed in saidimpedance which is dependent on said fixed inherent electrical quantity,the portion of said potential drop due to said fixed inherent electricalquantity constituting the reference potential of said power supply,voltage-dividing resistor means for applying a potential to said stageproportional to the potential existing across said load circuit, andmeans for applying the potential existing across said impedance to thecontrol electrode of said control transducer.

A voltage-regulated power supply comprising, a source .of direct-currentpotential, a load circuit connected to said source, an electronicdischarge tube having at least a grid, cathode and anode, said cathodeand anode being interposed in series between said source and said load,an electrical amplifying device having at least one stage generating afixed inherent electrical quantity, an impedance connected in serieswith said stage and a source of direct current whereby a potential dropis developed in said impedance which is dependent on said fixed inherentelectrical quantity, the portion of said potential drop due to saidfixed inherent electrical quantity constituting the reference potentialof said power supply, voltage-dividing resistor means for applying apotential to said stage proportional to the potential existing acrosssaid load circuit, and means for controlling said grid by the potentialexisting across said impedance, the sense of control being such as totend to maintain constant potential across said load circuit.

4. A voltage-regulated power supply comprising, a source ofdirect-current potential, a load circuit connected to said source, anelectronic discharge tube having at least a grid, cathode and anode,said cathode and anode being interposed in series between said sourceand said load, the anode being more positive than the cathode, anelectronic amplifier stage including discharge tube means having atleast a grid, cathode and anode, a source of fixed primary referencepotential, said source of fixed primary reference potential being aninherent part of the electronic discharge tube means of said amplifierstage, an impedance connected in series with said electronic dischargetube means and a source of direct current for developing a potentialdrop in said impedance which is dependent in par-t on said fixed primaryreference potential, that potential drop due to said fixed primaryreference potential constituting the reference potential of said powersupply, voltagedividing resistor means for applying a potential to saidamplifier stage proportional to the potential existing across said loadcircuit, and means for applying the potential of said impedance to thegrid of said electronic discharge tube in such sense as to tend tomaintain constant potential across said load circuit.

5. A voltage-regulated power supply comprising, a source ofdirect-current potential, a load circuit connected to said source, acontrol transducer having several electrodes including a controlelectrode for controlling an electrical quantity existing between a pairof other electrodes, said pair of electrodes being interposed in seriesbetween said source and said load, an electronic amplifier stageincluding discharge tube means having at least a grid, cathode andanode, said discharge tube means generating a fixed inherent potential,an impedance connected in series with said stage and a source of directcurrent for developing a potential drop in said impedance which isdependent in part on said fixed inherent poten tial, that portion ofsaid potential drop due to said fixed inherent potential constitutingthe reference potential of said power supply, voltage-dividing resistormeans for applying a potential to said stage proportional to thepotential existing across said load circuit, and means for applying thepotential across said impedance to the control electrode of said controltransducer is such sense as to tend to maintain constant potentialacross said load circuit.

6. A voltage-regulated power supply comprising, a source ofdirect-current potential, a load circuit connected to said source, anelectronic discharge tube having at least a grid, cathode and anode,said cathode and anode being interposed in series between said sourceand said load, the anode being more positive than the cathode, anelectronic amplifier stage including discharge tube means having atleast a grid, cathode and anode, a source of fixed primary referencepotential, said source of fixed primary reference potential being aninherent part of the electronic discharge tube means of said amplifierstage, an impedance connected in series with said discharge tube meansand a source of direct current for developing a potential drop in saidimpedance which is dependent in part on said fixed primary referencepotential, that portion of said potential drop due to said fixed primaryreference potential constituting the reference potential of said powersupply, a triode discharge tube having anode, cathode and control grid,a circuit interconnecting the anode of said triode and said last-namedsource of direct current, the cathode of said triode and said dischargetube means being connected together and the control grid of said triodebeing connected to said cathodes whereby changes in the temperature ofthe cathode of said discharge tube means which tend to vary said fixedprimary reference potential are compensated by equal but oppositevariations due to similar temperature changes in said triode,voltage-dividing resistor means for applying a potential to saidamplifier stage proportional to the potential existing across said loadcircuit, and means for applying the potential of said impedance to thegrid of said electronic discharge tube in such sense as to tend tomaintain constant potential across said load circuit.

7. A voltage-regulated power supply comprising, a source ofdirect-current potential, a load circuit connected to said source, acontrol transducer having several electrodes including a controlelectrode for controlling an electrical quantity existing between a pairof other electrodes, said pair of other electrodes being interposed inseries between said source and said load circuit, a transistor amplifierstage including a transistor having at least three electrodes, saidtransistor generating a fixed inherent collector cutoff current, animpedance connected in series with said stage and a source of directcurrent for developing a potential drop in said impedance which isdependent in part on said collector cutoff current, that portion of saidpotential drop due to said fixed inherent collector cutoff currentconstituting the reference potential of said power supply,voltage-dividing resistor means for applying a potential to said stageproportional to the potential existing across said load circuit, andmeans for applying a potential in accordance with the potential acrosssaid impedance to the control electrode of said control transducer insuch sense as to tend to maintain constant potential across said loadcircuit.

8. A voltage-regulated power supply comprising, a source ofdirect-current potential, a load circuit connected to said source, anelectronic discharge tube having at least a grid, cathode and anode,said cathode and anode being interposed in series between said sourceand said load, the anode being more positive than the cathode, atransistor amplifier stage including a transistor having at least threeelectrodes, said transistor generating a fixed inherent collector cutoffcurrent, an impedance connected in series with said stage and a sourceof direct current for developing a potential drop in said impedancewhich is dependent in part on said collector cutoif current, thatportion of said potential drop due to said fixed inherent collectorcutoff current constituting the reference potential of said powersupply, voltage-dividing resistor means for applying a potential to saidstage proportional to the potential existing across said load circuit,and means for applying a potential in accordance with the potentialacross said impedance to the grid of said electronic discharge tube insuch sense as to tend to maintain constant potential across said loadcircuit.

9. A voltage-regulated power supply comprising, a source ofdirect-current potential, a load circuit connected to said source, atriode discharge tube having grid, cathode and anode electrodes, saidanode being connected to the positive terminal of said source and saidcathode being connected to said load circuit to interpose theanode-cathode circuit of said triode in series with said source and saidloadcircuit, a transistor amplifier stage including a transistor havingemitter, collector and base electrodes, said transistor generating afixed inherent collector cutoif current having a specific value for aselected collector bias potential when the emitter current is zero, aresistor connected between the collector of said transistor and a sourceof direct current for developing a potential drop therein which isdependent in part on said collector cutoff current, that portion of saidpotential drop due to said collector cutoff current constituting thereference potential of said power supply, a resistive voltage dividerhaving terminals connected across the input terminals of said loadcircuit, a connection from the slider of said voltage divider to thebase electrode of said transistor for applying a potential theretoproportional to the potential applied to said load circuit, and meansfor applying a potential representing the potential drop across saidresistor to the grid of said triode discharge tube in such sense as tomodify its anode-cathode current in such direction and amount as to tendto neutralize changes in load circuit potential due either to changes inload or to changes in the potential of said source of direct-currentpotential.

10. A voltage-regulated power supply in accordance with claim 9 in whichsaid transistor is of the n-p-n type having a common emitter circuit, inwhich said source of direct current is the positive input terminal ofsaid load circuit and in which said last-named means is a conductiveconnection from said collector electrode to the grid of said triode.

11. A voltage-regulated power supply in accordance with claim 9 in whichsaid transistor is of the p-n-p type having in a common emitter circuit,inwhich said source of direct current is the negative input terminal ofsaid load circuit and in which said last-named means is a transistoramplifier containing an odd number of stages.

12. A voltage-regulated power supply comprising, a source ofdirect-current potential, a load circuit connected to said source, atransistor having collector emitter and base electrodes, two of saidelectrodes being interposed in series between said source and said loadand the third of said electrodes serving as a control electrode tocontrol the passage of currrent between the first two electrodes, anelectrical amplifying device having at least one stage generating afixed inherent electrical quantity, an impedance connected in serieswith said stage and a source of direct current for developing apotential drop in said impedance which is dependent in part on inherentelectrical quantity, the portion of said potential drop due to saidfixed inherent electrical quantity constituting the reference potentialof said power supply, voltage-dividing resistor means for applying apotential to said stage proportional to the potential existing acrosssaid load circuit, and means for applying a potential representing .thepotential across said impedance to the control electrode of saidtransistor in such polarity as to control the transistor current in suchsense and magnitude as substantially to neutralize changes in potentialacross said load whether dueto changes of load or change of potential ofsaid source of direct-current potential.

13. A voltage-regulated power supply comprising, a source ofdirect-current potential, a load circuit connected to said source, ann-p-n series transistor having collector, emitter and base electrodes,said collector electrode being connected to the positive terminal ofsaid source of direct-current potential and said emitter electrode beingconnected to said load interposing the transistor in series betweensource and load, an amplifying n-p-n transistor having emitter,collector and base electrodes, said amplifying transistor generating afixed inherent collector cutoff current having a specific value'for aselected collector bias potential, a resistor connected between thecollector of said amplifying transistor'and the positive terminal ofsaid source of direct-current potential for developing a potential droptherein which is dependent in part on said fixed inherent collectorcutoff current, that portion of said potential drop dueto said collectorcutoff current constituting the reference potential of said powersupply, the emitter terrninal'of said amplifying transistor beingconnected to the negative terminal of said source of direct-currentpotential, a resistive voltage divider connected across the inputterminals of said load circuit, a connection from a silder adjustablypositioned on said voltage divider to the base electrode of saidtransistor for applying a potential proportional to that applied to saidload circuit, and means for applying a potential representing thepotential, drop across said resistor to the base electrode of saidseries transistor, the applied potential being in such sense as tocontrol the current of said series transistor to' neutralize changes inload circuit potential; I

No references cited.

